As the first Australians came to the continent?

The skeletons of people and archeological discoveries in Australia you can trace the history up until 50,000 years before the trail will disappear. Up to this point, apparently, in Australia, people were not. How people got there and when? When people first arrived on the continent and how they spread across the continent? The answers to these questions can be found in the DNA of Australian aborigines. Genetic research 111 aboriginal Australians, released last week, offers an interesting and in some ways, and unexpected look at their remarkable history.

All living indigenous Australians are descended from a single population of founders who arrived about 50,000 years ago, the research shows. They spread across the continent, along the coasts for many centuries. And yet for tens of thousands of years after that these populations have remained isolated and rarely intermingled.

DNA that is used in the new study, taken from the aboriginal hair, collected during expeditions that took place from 1926 to 1963. The Board for anthropological research at the University of Adelaide sent researchers to communities throughout Australia, where they collected a huge amount of information about the aboriginal languages, ceremonies, art, cosmology and genealogy.

Many indigenous Australians today no longer live where their ancestors lived. In the 1900's, the government forcibly brought many of their traditional lands and separated children with their families. Many aboriginal Australians moved to the cities far from the places in which he grew up.

Due to the age of the subjects and detailed reports, scientists have decided that hair samples can give a better idea of the pre-colonial past. "It seemed obvious that this collection is perhaps the best way to restore Australian history," says Alan Docked, DNA researcher from the University of Adelaide.

First he and his colleagues sought consent to testing from the descendants of people whose hair samples were collected. They traveled to aboriginal communities, spending several days in communicating with family members to help them in solving problems. All but one of the families that they visited, gave them permission to conduct research.

Dr. Cooper and his colleagues knew that DNA extraction would be difficult. For many decades, until the hair was in storage, the genetic traces could be destroyed beyond recognition. Worse, the hair was cut off with scissors. The best way to get genetic material from strands of hair to pull it from rich DNA root.

Given these uncertainties, the researchers decided to increase the chances of success by finding rich mitochondrial DNA is located outside the cell nucleus and is inherited solely from the mother. In the end, the scientists were able to gather together all mitochondrial genes in each of the hair samples.

Comparing the native sequence with DNA from other parts of the world, scientists have determined that they all belong to one human lineage, which means that all aborigines are descended from a single migration into the continent.

Mitochondrial DNA gradually accumulates mutations with approximately the same speed, like the ticking of the molecular clock. Summing up the mutations in the hair samples, the scientists also estimated that their owners are all descended from a common ancestor, who lived about 50,000 years ago. This finding converges well with the estimated age of the oldest archaeological sites in Australia.

The Mitochondrial tree has also provided clues to how humans spread across the continent.

Fifty thousand years ago the sea level was so low that Australia and New Guinea formed a single continent. People moved from Southeast Asia to the mainland; some settled in the present New Guinea, the others went further South to Australia.

They kept to the coastlines, until it reached South Australia about 49 000 years ago. But as soon as the large resettlement ended, according to new research, the ancestors of modern aborigines were sitting in their houses for tens of thousands of years.

Mitochondrial DNA contains no evidence that these populations are mixed any significant way, which surprised scientists. "We expected that all areas will be completely diverse mix of people," says Cooper.

This is not the model of migration, which is documented on genes on other continents. In Europe, for example, new peoples settled every few thousand years, mixing with the societies they encountered.

The Difference is visible on agriculture, says Cooper. Unlike Africa, Asia, and Europe, Australia has not experienced the rise of agriculture a few thousand years ago. "If you have no cheap carbs, you can't increase the population," he said.

The Population grew in other continents, but are often at risk of catastrophic crop failures. When this happened, the answer was only one: a mass migration.

In Australia the aborigines did not rely on the harvest and lived as nomads in some regions. They have never felt the need to cross the continent.

"This is really amazing, but at the same time is undeniable," says Stefan Sheffels, population geneticist from the Institute of human history, max Planck in Germany, who did not participate in the study. "The data say about it."

Peter Bellwood, an archaeologist at the Australian national University, also not involved in the study said that most of the new data corresponds to the archaeological data. But he was difficult to understand, as Australians, aborigines were able to stay so long settled.

He points to the tools that were used by many native cultures across great distances, as well as seven languages spoken by many indigenous peoples. Dr. Bellwood doubt that they could have spread so far without the people.

"If people are not moved, why the languages and tools should be?", he said.

Dr. Sheffels and other scientists have expressed the view that mitochondrial DNA is missing important parts of Australian history. DNA in the nucleus of each cell received from both parents, may hold a key to a wider range of data.

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